How long will it take: the elusive sum of all parts

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How long will it take you to do it?

When will you get it done?

What is the task duration?

How many times have you had to answer such questions? How often was your answer proven to be just right? And how often are you tempted to say “it depends”?

Let’s chat about why. Why “it depends”?

Here are some reflections from my typical morning. I have children and work full time, so I have to be very organized. No other choice. I have to get breakfast ready on time, and lunchboxes are a mandatory requirement. Kids need to be out by certain time as the school bus will not wait. I don’t like 9am meetings but have them almost every day. So I have to plan every minute of my morning, and I need to start early enough so that everyone and everything is ready by the bus arrival time.

Pure work-back planning. I’ve done it for years now. I should know how long it takes, up to a minute. In fact, I should be putting my Six Sigma Green Belt to a good use as this is such a repeatable process, right?

Then why some mornings feel so out of control? My alarm clock goes off at the same time, but nothing comes together without a struggle. The clock moves too fast, the same task takes twice as long, and I’m late for the same 9am meeting that I made on time yesterday.

So what does this all have to do with project task estimation? There is no escaping the analogy. Whether you have children or not, the task duration in your repeatable morning routine will have variances. Will these variances be statistically significant or not? The answer is, of course, “it depends”.

  • It depends on when I start.

On Saturdays, I start 30 minutes later than on weekdays. Somehow these extra 30 minutes of sleep make a huge difference to my productivity and speed of execution.

If you are planning to start an important project activity on a Friday or two days before a holiday, or at 11:30 when people start thinking about lunch, the task duration variance is almost inevitable.

  • It depends on the pre-requisites.

This will take exactly X minutes (or hours) of pure work effort, assuming everything is ready. But is everything always ready? What if I forgot to wash the lunch containers last night? Three minutes before I can start filling them again. What if there are no teabags in the usual place? An extra minute to get a new box from the pantry.

Pre-requisites are not always there when you need them, or may have been forgotten during planning. If half of the test data is missing, the test case execution will be delayed by the time required to discover what is missing, getting it and putting it in place.

  • It depends on task variations.

Yes, I usually cut up some fruits in the morning. But it’s not always the same fruits – it’s whatever we have. Apples and pears are quick, strawberries may take longer if they did not travel well. Kiwis require pealing and blueberries are just wash and go, unless I drop some on the floor. So it could be 2 minutes but could be twice as long, which makes up a 100% variance.

Even with small tasks in the work breakdown structure, expect variances to go in one direction and to add up. The further out you plan, the less you can predict task variations.

  • It depends on whether I have to multitask.

I do multitask, but only to a point, and it takes practice. Multitasking works best with things I can do with my eyes closed. For a new activity or something that may pose a safety risk, multitasking is not only an illusion, but can be harmful. For example, I stop cutting vegetables if I need to focus on kids’ school troubles or arguments. And I really focus on pouring boiling water, especially if I only slept five hours.

If you have a valuable resource assigned to four activities because each one “should take less than two hours a day and they can be done in parallel”, you have to expect that something will have to give, especially if certain activities are not routine and require particular concentration and focus.

  • It depends on the number of transitions.

Moving from one task to another has duration. I may need to put down a utensil, cross the kitchen, and think for a moment about what I was planning to put into the lunchboxes today (I did remember just a moment ago, but drawing a blank now). Or, the act of completion may generate an unplanned step. For example, a broken apple piece may go into my lunchbox so that it does not go to waste – so, step aside to get another container, and then I should probably add a few more pieces to make it a worthwhile snack. Just spent an extra minute on this (with a benefit to my healthy eating).

Do not rely on arithmetic to add task duration. 7 tasks of 2 hours each will not add up to two days – expect at least three days if not more.

  • It depends on whether anyone is helping me.

When I am beating omelettes, heating up pasta for thermoses and brewing tea all at the same time, I prefer that nobody tries to help me. I calculate my movements and utilize each step: I will move towards the microwave just as it starts beeping and will have the tea bag ready when I hear the kettle is about to boil. Paying attention to a helper, giving them directions, or walking around them takes extra time, and doing some tasks is actually faster than coherently explaining to someone else what needs to be done.

If an expert estimates a task duration of 2 days, you cannot assume that putting two people on this tasks will cut the time in half. Dividing the work, communicating, handing off and putting the results together takes extra time, and it is hard to estimate how much. That will depend on the compatibility of the workers, how well they know each other and their relative competence.

  • It depends on how I’m feeling.

Some days are just slow.  I can be tired, upset or recovering from a cold. I may have had a sleepless night. Need I say more?

Tasks are executed by people who will have variances in their productivity due to natural human reasons. Just like the project manager might.

  •  It depends on whether I am rushed.

If I get up ten minutes late, I sometimes end up twenty minutes behind. First, I am flustered because I started late, then I try to cut corners, which ends up in mistakes that need to be fixed. Dropping a raw egg on the floor because I’m in a hurry can set me back so much that the breakfast will have to be a bagel to go.

Some people thrive under the deadline, but for many others, rushing causes them to slow down and make mistakes. Do not expect quality when compressing duration to fit the remaining time – just don’t.

 * * *

Estimation is not precise. It is not the same as measurement. We can estimate, then record the facts, and then model the accuracy of our estimations, however the factors that will impact future will still have unpredictability to them. Not only the duration of tasks will vary, but inevitably some missed tasks will emerge at a later stage once there is more information available.

Without reasonable contingency, a project will create a stressful environment and unreasonable expectations, and the results will invariably disappoint. And let’s not underestimate the required contingency.

Please share your thoughts!

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